In MDL-51374 we start passing an array with the modified tablenames to moodle_database::reset_caches, if there is any modification in any non temp table we are purging (delete all cache entries) the whole databasemeta application cache, would be better to use delete($tablename) instead, we should look at what to do with moodle_database::tables and moodle_database::metacache

If you are going to work on this issue you might be interested in reading https://tracker.moodle.org/browse/MDL-51374?focusedCommentId=400249&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-400249. #1 was implemented as part of MDL-51374